The present invention is generally related to light sources, and more particularly to traffic signal lights including those incorporating solid state light sources.
Traffic signal lights have been around for years and are used to efficiently control traffic through intersections. While traffic signals have been around for years, improvements continue to be made in the areas of traffic signal light control algorithms, traffic volume detection, and emergency vehicle detection.
One of the current needs with respect to traffic signal lights is the ability to generate a homogenous narrow light beam, that is, a coherent light beam having a uniform intensity thereacross. Conventional incandescent lights tend to generate a light beam having a greater intensity at the center portion than the outer portions of the light beam. With respect to current solid state light sources, while LED arrays are now starting to be implemented, the light output of these devices can have non uniform beam intensities, due to optics and when one or more LEDs have failed.
One current approach to adjust the viewing angle of an incandescent traffic signal is to simply mask the active area of an incandescent illuminated diffuser. The masking is typically accomplished by the use of a reflective tape similar to duct tape. This approach is tedious, trial-and-error, and problematic.
There is desired an improved solid state light source generating and steering a homogenous light beam.
The present invention achieves technical advantages as a solid state light generating a homogenous steerable light beam particularly useful in traffic control signals.
The solid state light includes a housing having a cavity, an area array of light emitting diodes (LEDs) disposed in the housing cavity and generating a light beam, and a lens disposed over the LED area array transmitting the received light beam. Advantageously, a mask is selectively positionable over the cavity and selectively blocks a portion of the light generated by the LEDs to thereby responsively control a direction of the light beam transmitted through the lens. The unmasked light beam is transmitted through the lens at an angle being a function of a position of the mask and the lens optics. Preferably, the housing cavity has light reflective side walls and a light diffuser disposed over the cavity and transmitting the light beam. Preferably, the light diffuser comprises a holographic light diffuser. The plurality of LEDs disposed in the housing cavity preferably are comprised of a first set emitting light at a first color, such as green, and a second set of LEDs emitting light at a second color, such as yellow light. Advantageously, the green LEDs and the yellow LEDs can be alternatively driven to establish the desired light from a single LED cavity.
The mask is selectively positionable over the LED area array in at least one dimension, and preferably in two dimensions. The mask may comprise of a template having an opening permitting only a portion of the light to be transmitted therethrough. This template may be keyed with respect to the housing for accurate alignment of the mask opening with respect to the area array of LEDs thereunder. The template may be secured using a Velcro(copyright) material or the like.
The mask, in combination with the lens optical characteristics and orientation, determines the angle of the light emitted through the lens. The mask, in combination with the lens, also determines the shape of the emitted light beam. Preferably, the light beam is adjustable +/xe2x88x9220xc2x0 with respect to normal from the LED in the first dimension, and +/xe2x88x9210xc2x0 in the second dimension.